Rheostat



March 4, 1941. w. L. BLISS 2,234,155

RHEOSTAT Filed Jan. 21, 19358 2 Sheets-Sheet 1 INVENTOR ZVoLLILam$.B6Q;- BY X7 1 4 W. L. BLISS March 4, 1941.

RHEOSTAT Filed Jan. 21, 1938 2 Sheets-Sheet 2 ATTORNEY Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE RHEOSTAT William L. Bliss, Niagara Falls, N. Y., assignor to USL Battery Corporation, Niagara Falls, N. Y., a corporation of New York Application January 21, 1938, Serial No. 186,210

2 Claims. (01. 201-48) This invention relates to rheostats, or variable Fig. 5 is a partial section of Fig. 4. resistances. Fig. 6 shows a flexible conductor by which An object of my invention is to provide a means one end of the resistance wire is aifixed rheostat that may be inexpensively constructed. to a support.

5 Another object is to provide a means for in- Fig. 7 shows means by which the other end of 5 troducing into a circuit a resistance without an the resistance wire is affixed to its support. appreciable amount of arcing at the contact Fig. 8 is a detailed sectional view of a pulley points between said circuit and said resistance. and the resistance helix in contact therewith.

A further object is to provide a simple and Reference numeral I0 indicates a transverse effective means for cutting into and cutting out supporting member from which a vertical mem- 10 of a circuit a varying amount of resistance wire. ber ll depends, the two members forming a frame With these and other objects in View, one in the shape of a T upon which the rheostat may embodiment of my invention contemplates a be mounted. The frame may be made of any flexible resistance element, or a series of such suitable material; it has been found convenient elements, a fixed electrical contact at one end to employ wood for member I!) and an ordinary 15 thereof, a second electrical contact member electrical conduit of metallic tubing for member adapted to contact the resistance element at H, in which may be inserted a fuse socket l2, more than one point at any one time, such as asnap switch [3, and an ammeter M.

a pulley which may be in contact with several Fastened to member ID are two hooks, l5 and turns of a flexible helical resistance element at IS, a fuse block I! and apulley I8. 20 one time, and means for varying the relative The resistance unit consists of a helix IQ of positions of said resistance and said second conwire of suitable high resistance alloy, such as tact member. By virtue of such an arrangement, nichrome, one end of said helix being afiixed under the proper conditions of tension, the flexito a flexible low resistance conductor 20 which ble resistance will conform itself to the configurain turn hangs from hook l5, and the other end 25 tion of the second contact member, so that there being affixed to a chain 21 depending from will be a number of points of mutual contact. hook Hi.

In the above-cited instance of a pulley and a From a point intermediate of the ends of horihelix, if there be several points of contact bezontal member ID, depends pulley l8 through tween the two, that amount of current flowing which helix l9 passes, so that, as shown in Fig. 1, 30 through any one contact will be considerably the helix being supported at some point interless than the total current in the circuit and, as mediate both ends, it may hang in two loops 23 any contact is broken, the amount of arcing and 24 in the general form of aW. which accompanies the break, is very much less Pulleys 25 and 26 ride on the helix at the botthan if the total amount of current were intertom of each of the loops and are connected to 35 rupted as the contact member moved from one each other by suitable means such as a rope 21, part of the resistance to another. Moreover, which passes through a pulley 28 extending upthere is much less wear in the resistance wire wardly from a. point near the lower end of verwhen a rolling contact is employed, rather than tical member II. The rope is adjusted so that a sliding contact. the helix is under sufficient tension to keep the 49 Other objects, features and advantages of this adjacent turns thereof separated from one aninvention will be apparent from the following other. description and appended drawings, in which As here illustrated, that part of the helix which like reference numerals indicate like parts of is more remote from the fixed terminal thereof,

that embodiment of the invention herein shown or the right hand part of the helix, as viewed in 45 and described, Fig. 1, may be of a lighter, higher resistance wire In the accompanying drawings: formed into a helix of somewhat reduced diam- Fig. 1 is an elevation of a rheostat comprising eter, for the current in the circuit is, of course, the subject matter of this invention. much less when most of the resistance is cut in; 50 Fig. 2 is an elevation of the same with all the consequently, the more remote wire is called upon 50 resistance cut out of the circuit. only to handle the lighter currents, and by using Fig. 3 is a diagrammatic representation of the a lighter wire, a considerable saving is effected in electrical circuit involved therein. the cost of manufacturing. The lighter wire 29,

Fig. 4 is a detailed view showing the junction and the heavier one 30, may be joined together of two helices of different diameter. as shown in Figs. 4 and 5, by making the outside 65 diameter of the helix of the former just enough larger than the inside diameter of the latter that the one may be screwed into the latter, the turns of the helix serving as threads. To prevent excessive bending strains at this junction, it has been found advisable to insert within the smaller helix, 9. third helix 3| which acts as a reinforcement or stiffener at this point.

Fig. 3 shows the wiring diagram for the rheostat. Numeral 32 indicates the direct current power line to which the rheostat is connected in series with the load. It will be seen that from the positive wire of power line 32, the current flows through one of the two fuses 33 inserted in fuse block I1, through flexible conductor 20 and that part of the resistance helix which hangs in loop 23, through pulley l8, fuse 34 in fuse socket I2, and ammeter M, to the positive side of the load. From the load it returns to the negative line of the power line, through the other one of the fuses 33. It will be seen from Figs. 1 and 2 that loop 23 may be enlarged or diminished by appropriate manipulation of the rope 21, thereby increasing or lessening the resistance of the circuit. Flexible conductor 20 is of such length that it will extend from hook l5 to pulley I8 when it is desired to eliminate entirely the high resistance helix from the circuit as shown in Fig. 2.

Fig. 6 shows in detail the construction of flexible conductor 20, which is merely a multi-strand copper Wire, one end of which is looped over the last turn of the helix 1!! and the other end of which is affixed to a clip 35 which may engage hook l5, as well as bind the loose ends of the conductor and furnish means for soldering or otherwise electrically connecting thereto Wire 36 leading to the power line.

Rather than connecting the other end of the helix directly to hook [6, in which event that portion of the helix adjacent thereto could never enter into the electrical circuit, it has been found more economical to substitute therefor a short length of chainor other suitable tension member designated by reference numeral 2| and shown in detail in Fig; 7. The chain is fastened to hook l6 by means of an intermediate hook 31 and swivel joint 38 which permits relief from any strains in the helix occasioned by its tendency to unwind or wind. 1

It will be observed from Fig. ,8 that the variable contact between the resistance wire and the load in this rheostat is effected between the helix and the pulley and is of rolling rather than of sliding nature. Moreover, inasmuch as several turns of the helix l9 are in contact with the pulley 18 at any one time during adjustment of the rheostat, only one current path of several in parallel is broken at any instant, and the current in that path being only a fraction of the total, the arcing between and the subsequent corrosion of the contacting members will be greatly reduced.

Although I have shown and described only one embodiment of my invention, it is understood that various additions thereto, modifications thereof, and changes in the shape, size, and arrangement of parts or other details of construction may be made or effected without departing from the spirit of my invention or the scope of the subjoined claims,

I claim:

1. In a device of the class described, a. support, a relatively long flexible resistance suspended by its ends from spaced points in said support, said resistance being helical in form and adapted to be longitudinally resilient, a grooved contact member cooperating with the resistance at predetermined points along its length, a flexible cord-like member movable about a point spaced from the contact member and having its ends co operating with the resistance adjacent the sides of the contact member, said cord-likc member under manual manipulation being adapted to change the position of the'resistance with relation to the contact member and to maintain the resistance under longitudinal tension so as to bear firmly against the contact member to give a good contactual relation therebetween, and an electrical circuit between one end of the resistance and the contact member.

2. In a device of the class described, an overhead support, an elongated resistance member supported at its ends at spaced points in said overhead support and depending therefrom, an auxiliary supporting member of electrical conducting material secured to said overhead sup port between said spaced points, over which said elongated resistance passes, whereby said resistance member is caused to assume a double-U configuration, said resistance member being in electrical contact with said auxiliary supporting member, elongated manually operable means positioned in the lower portion of each U of said resistance member and passing around a fixed point spaced downwardly from said resistance member for holding said resistance member in firm contact with said auxiliary support, and an electrical circuit connected to one end of said resistance member and said auxiliary support member whereby the amount of resistance in said circuit may be varied by manipulating said manually operable means to vary the relative lengths of said U-portions of said resistance member.

WILLIAM L. BLISS. 

